Abstract: A solar blind optical filter which absorbs solar UV radiation and transmits non-solar UV radiation includes a carrier material and a salt of a dithioic acid of the formula RCS.sub.2.sup.- X.sup.+ wherein R is an a organic substituent that does not absorb ultraviolet light at wavelengths between 260 nanometers and 300 nanometers and X is a counterion. The solar blind optical filters of the present invention are useful for observing non-solar ultraviolet radiation in the presence of solar radiation.